ANALYSIS OF THE WORM GEARING

Let us carry out the analysis of the worm gearing for strength if torque at the worm shaft T^w=105 N×m; torque at the gear shaft T^g = 1750 N×m; rotational speed of the worm shaft n^w =441.75 rpm,rotational speed of the gear shaft n^g = 22.1 rpm; velocity ratio of the gearing u=20.

6.1. Determine approximately the slippage speed in the worm gearing

,

where n^w is the rotational speed of the worm in rpm; T^g is the torque at the worm gear shaft in N·m.

6.2. Select the material of the worm and the worm gear.

Worm

The best performance is obtained when worms are made of carbon or alloy steels of grade Steel 45 (0.45 C) and Steel 40XH (0.40-C-Cr-Ni) surface-hardened to hardness ranged from 50 to 55 HRC or of grade Steel 20X (0.20 C-Cr) and Steel 18XГТ (0.18 C-Cr-Mn-Ti) case-hardened to hardness ranged from 58 to 63 HRC. The immunity to seizure improves with increasing hardness of the working surfaces of threads. Also, the surface roughness of the threads should be kept to a minimum (usually Ra 0.2). For this purpose the threads are ground and polished.